Transmission regulator system



March 15, 1932. D, DUTTQN TRANSMISSION REGULATOR SYSTEM Filed March 11, 1930 ATTORNEY Patented Mar. 15, 1932 UN TED ST res 'PATENTYOFFICE 'rnoivms nnur'roiv, or CHEVY CHASE Gnmmns, MARYLAND, 'ASSIGNOR 'ro 'mnnIoAN TELEPHONE AND TELEGRAPH COMPANY, A oonromvrroiv or new YORK msmssm 313G1 ATO'R .VSY-STEM Application filed Marcli- 11, 1930. Serial No. 435,000.

This invention relates to signaling systems and particularly to those employing repeat-' ers to adjust the magnitude of transmitted signals. More particularly, this invention relates to arrangements for automatically adjusting the gain of a repeater in order to compensate for variations in the transmission equivalent of one or more conductors forming a circuit when the temperature of. these conductors changes under varying atmosductors, it has been determined that variable temperature is an important factor in-changing the effective attenuation of the circuit.

20 At high temperatures, the attenuation is quite large and, conversely, it is low at low temperatures. A pilot wire is often set aside in a cable andthis wire forms a. circuit which is connected to a repeater so that the gain of therepeater may be changed in accordance with variations in the temperature of the.

pilot wire. It is the purpose of the arrangement to increase the gain of the repeater when 1.

the resistance changes by virtue of an increase in temperature and to decrease its gain with a decrease in temperature. 7 It is an obj ectofthis invention to provide a pilot wire-regulating system intended for use with the repeaters of signaling systems to automatically adjust the gain of each repeater so as to take care of temperature changes which bring about variations in the transmission equivalent of the conductors forming the signaling circuit. This obj ect may becarried out with the apparatus shown in the drawing, details of which willnow be described. p

Referring to the drawing, the reference character W designates two conductors forming a cable pair or circuit. Such a pair or'circuit is known as a pilotwire. It may be saidof this pilot wire, aswell as ot each of the other conductors of the cable, that its resista-nce changes in accordance with temperattire. It is welllmown thatan increase in temperature causes a decrease in the trans mission loss. I

The pilot wire W isiconnected: in series circuit whichincludes a battery B anda resistance R It will be apparent that as the resistance increases and, consequently,'the

flow of current from battery 13 through the resistance R will decrease. Conversely, a decrease 1n temperature wlllcause a greater h flow of current from battery B through the resistance R A vacuum tube designated V includes three electrodes, agrid electrode 9 a plate electrode p and a filament electrode f The grid electrode is connected to the filament electrode through the resistance R f anda battery-1B A battery B is connected across the filament electrode 7, and one side'of this battery is grounded. The plate electrode 10 and the filament electrode are: connected ina'cir- -.cuit which includes, in addition to theseelements, a battery B4, a resistance R2,;abattery B and ground. The resistanceR is shunted by a condenser G.

The reference character .Vg designates a vacuum tube which includes four elements,

a plate electrode p a filament electrode 7%,- a grid electrode 9 and a. screen gridv electrodes. The grid electrode 9 is connected tothe' filament electrode f through a winding'L; and a battery B this battery being employed ior biasing the .grid electrode 9 at a suitable negative potential with respect to the. filament electrode f The plate electemperature of the pilot wire increases, its

trode p is connected to the filamentielectrode f through a winding L and a battery B-,,'the

battery l3 providing a suitable positive po-' tential for the plate electrode 10 The fila- I ment f is connected to a battery B one ter- -minal of which is grounded. The screen grid electrode 8 is connected to the negativepterminal of battery B through a'choke coil K This screen grid electrode may be maintained at a positive potential and the magnitude of this positive potential may be changed in order to correspondingly vary the. gain of the .vacuum; tube V i V Themannerin which: the" gain of the vacuum tube may be controlled will be described in greater detail hereinafter.

A winding L is connected to a source of signals E and the signals that reach the winding L may be of the voice frequency type or carrier current modulations corresponding to voice frequency signals or of any other type. Windings L and L are inductively related to each other and the winding L transmits the currents impressed upon the winding L through the circuits associated with the vacuum tube V to a winding L The winding L is inductively related to winding L and, moreover, it transmits the signals amplified by the vacuum tube V to an output circuit E The degree of amplification of the vacuum tube V 2 is determined by the relative potential of its screen grid electrode 8. As the positive potential of the screen grid electrode increases, the amplification of the vacuum tube will increase and upon a decrease in the positive potential of the screen grid electrode 8, the amplification of the tube will be correspondingly decreased. Thus, it will be apparent that the gain in the signals transmitted 7 from the source E to the circuit E may be changed by any desired amount merely by the control in the size of the potential impressed upon the screen grid electrode 8.

Under normal conditions of temperature, the flow of current from battery B through resistance R will produce a potential difference across resistance R which opposes the voltage established by the battery B Under normal conditions, the voltage of the battery B is greater than the potential difierence across the resistance R and the difference between these voltages determines the negative potential impressed upon the grid electrode 9 of the vacuum tube V with respect to the filament electrode f of that tube. The vacuum tube V is operated on the straight line portion of its plate current-grid voltage characteristic curve in order that any change in the effective potential of grid electrode 9 will cause a corresponding change in the thermionic emission between the filament electrode f and the plate electrode 39 of the tube V When there is a decrease in the temperature of the pilot wire l/V the potential creased. Similarly, an increase in temperature will decrease the potential difierence across resistance R correspondingly increasing the negative potential of the grid electrode 9 of the tube V with respect to its filament electrode f and correspondingly decreaslng the flow of current in the plate circuit ofthe tube V So, it will be seen that the flow of current through the resistance R which is in the plate circuit of the vacuum tube V changes in accordance with the temperature of the pilot wire An increase in temperature brings about a decrease in the current flowing through resistance R and a decrease in temperature produces an increase in the flow of current through resistance R The screen grid electrode 8 of the vacuum tube V is'connectedin series with choke coil K resistance R battery B and ground. The battery B and the magnitude of the current flowing through the resistance R determine the effective potential of the screen grid electrode 8. When the current flowing through resistance R increases as a result of a decrease in the temperature of the pilot wire tial of the screen grid electrode 8 will be.

dropped below its normal value. Similarly,a decrease inthe flow of current through resistance R as a result of an increase in the temperature of the pilot wire W will increase the positive potential of the screen grid electrode 8 above its normal value. Thus, the gain of the repeater which includes the vacuum tube V2 will be increased when the temperature of the pilot wire increases and the gain will decrease as the temperature of the pilot wire decreases.

The screen grid electrode of another vacuum tube V is connected in series with the resistance R battery B and ground. The

gain of the repeater which includes this vac and has. a great many advantages over those' regulating systems known in the art. It employs no relays or moving parts and, consequently, there can be no trouble due to the sticking of contacts or due to dirty or corroded contacts. The complete absence of moving parts eliminates mechanical difliculties. Moreover, changes in the gain of the repeaters are made gradually and not step by step. Furthermore, the cost of installation as well as the cost of maintenance will be considerably smaller than that of any repeater regulating arrangement now used in the art.

While this invention has been shown in a certain particular arrangement merely for the purpose of illustration, it will beunderrepeaters or groups of stood that the general principles of this invention may be applied to other and widely varied organizations Without departing from the spirit of the invention'and the scope of the appended claims. What isclaimed is:

1. A gain control system including a first trode of the first tube through the second source of direct current potential, a second resistance connected between the grid and filament electrodes of the first tube, and a source supplying direct current potentials which vary in accordance with temperature, the latter source being connected in series with said second resistance.

2. A gain control system including a first tube having plate, filament and grid electrodes, a first resistance connected between the grid and filament electrodes of said tube, a second vacuum tube having plate, filament,

grid and screen grid electrodes, the filament electrodes of both tubes having a common connection, an input circuit connected between the grid and filament electrodes of said second tube, an outputcircuit connected between the plate and filament electrodes of said second tube, the screen grid electrode of the second tube being connected to the plate electrode of the first tube, a second resistance, a source of potential connected in series with said second resistance and the plate and filament electrodes of the first tube, and a pilot wire connected in series with the first resistance. V

3. A gain control system for a plurality of repeaters each of which includes a tube having plate, filament, grid and screen grid electrodes, including a three-element tube having plate, filament and grid electrodes, a first resistance connected between the plate and filament electrodes of said three-element tube, all of the screen grid electrodes being connectedto the filament electrode of said three- 1 element tube through said firstresistance, a second resistance connected between the grid 2 and filament electrodes of said three-element name to this specification this 4th day of March, 1930.

THOMAS D. DUTTON. 

